ANSWERS

Process of Science

How Do Cells Communicate with Each Other?

Lab Notebook

Aggregation Test / Number of Plates with Aggregation / Number of Plates without Aggregation / % Aggregation
Temperature Change / 4 / 4 / 50%
Food Depletion / 7 / 1 / 88%
Water Depletion / 6 / 2 / 75%

Molecule Identification Tests

Aggregation Test / Number of Plates with Aggregation / Number of Plates without Aggregation / % Aggregation
Treated with Protease / 7 / 1 / 88%
Not Treated with Protease / 7 / 1 / 88%
Treated with Solvent / 0 / 8 / 0%
Not Treated with Solvent / 7 / 1 / 88%
Colorimetric Tests / Number of Flasks with Positive Test / Number of Flasks with Negative Test / % Positive
Carbohydrate Test / 0 / 8 / 0%
Nucleotide Test / 7 / 1 / 88%
cAMP Confirmation Test / Number of Plates with Aggregation / Number of Plates without Aggregation / % Aggregation
cAMP Treatment / 7 / 1 / 88%

Questions

1. Provide two reasons why communication is essential between cells in multicellular organisms.

Cell to cell communication in multicellular organisms is needed to: 1) organize the body for development and growth, and 2) achieve homeostasis by coordinating functions carried out by different cells.

2. Which environmental factor produced the strongest aggregation response? Explain why you believe this factor had the strongest effect.

Depleting the food supply had the strongest aggregation effect. The cellular slime mold enters dormancy during aggregation to avoid unfavorable environmental conditions. Changes in temperature and water supply may be temporary. Thus, some of the slime molds keep feeding with the risk of dying if the environmental conditions do not improve. Probably, the loss of food is a sign of more severe environmental change, and nutrition is needed to keep the cells active. So, it is beneficial to go dormant and become active when food becomes abundant again.

3. What can you conclude about the chemical nature of the aggregation molecule?

The aggregation molecule is not a protein or a lipid. It is a carbohydrate, nucleotide, or another chemical compound.

4. What has this investigation told you about the aggregation molecule and what more do you need to know about the chemistry of the molecule?

The molecule is a nucleotide. Further investigation is needed to determine the particular type of nucleotide that is being used for cell communication. The way the nucleotide signals the target cells must also be investigated.

5. From your data, which nucleotide best matches the aggregation molecule, and what needs to be done to confirm your answer?

The travel time suggests that the aggregation molecule is cAMP. To confirm this, cAMP should be tested on slime molds to see if it causes aggregation.

6. What conclusion can you make from the information you gathered from the entire experiment?

It can be concluded from all the data that cAMP is the molecule that causes aggregation of slime molds.

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